1. Field of the Invention
The present invention is generally directed to the field of detecting leaks from underwater systems, and, more particularly, to an intelligent underwater leak detection system for detecting leaks from subsea systems and structures.
2. Description of the Related Art
There are many existing subsea production systems and structures that are employed in the production of oil and gas from subsea wells. Due to environmental, regulatory and perhaps safety regulations, it is important to be able to readily detect the leakage of undesirable materials from such subsea systems. For example, the detection of leaks of hydrocarbons or hydraulic fluid and/or other chemicals from such underwater systems is very important as it enhances the environmental and operational efficiency of such subsea systems, e.g., subsea hydrocarbon production facilities.
Many techniques have been employed to attempt to detect undesirable leakage of material from such subsea systems. For example, it is known in the prior art to employ acoustic, fluorescence, temperature and gas based measurement systems to detect such leaks. Each of these leak detection methods have their strengths and weaknesses as it relates to detecting leaks. In short, while each of these leak detection methods have applications where they are acceptable, none of them are, individually, capable of efficiently detecting leaks in all applications. In most cases, such leak detection systems are non-permanent in nature in that they are typically used during periodic survey operations. In some cases, however, such systems were permanently positioned subsea adjacent the subsea system being monitored.
The majority of underwater fluorescence, temperature and gas sensors used for leak detection have a very small or limited field of sensing capability. That is, they are essentially point sensors. In the case of temperature and gas sensors, such devices are typically only capable of making measurements at the actual sensing device. Some fluorescence sensors have slightly greater range than temperature or gas sensors, but it is still very limited. For example, FIG. 1 is a schematic depiction of a prior art fluorescence point sensor device 10 with a very small sensing field depicted by the circle 12, e.g., approximately 2 cm. Thus, such fluorescence based systems typically only sense a relatively small volume of water. Other fluorescence sensors, such as those shown in, for example, UK patent application GB 2405467 and U.S. Pat. No. 4,178,512, do have a greater range.
The limited sensing range of prior art fluorescence, temperature and gas based sensors can be detrimental to the detection of leaking materials. For example, employing leak detection sensors with such a limited range means that, in order to be detected, the plume of leaking material has to actually reach such sensors before it can be detected. This means that a very large number of permanent sensors of this nature would need to be employed to effectively monitor an underwater production system. Obviously, deploying a large number of permanent point-type sensors to effectively monitor a subsea facility would be very expensive and would pose a number of practical problems relating to the deployment of such sensors, as well as providing power and data communication with such sensors. Additionally, such fluorescence sensors can, by definition, only detect leaking material that fluoresces, thus making such sensors ineffective for detecting leaking materials such as gas or water.
On the other hand, acoustic based leak detection devices are capable of detecting leaks in a larger area via the noise that may be produced by material leaking from the underwater structures. However, such acoustic system only detect a secondary effect of the leak, i.e., noise. The performance capability of such acoustic systems may be severely restricted in noisy environments. Such acoustic systems are generally not able to precisely locate the source of the leak. Moreover, the acoustic based systems are unable to differentiate between leaking materials.
Temperature sensors are likewise not able to differentiate between leaking materials. Temperature sensors also may have a limited effective range, especially as it relates to the detection of relatively small leaks. On the other hand, gas sensors can differentiate between various leaking materials, but they typically have a very limited range.
The breakage or movement of components of a subsea facility, such as pipes, may provide direct evidence of a leak location or information on potential future leak sites. In some cases, such breakage or movement can be visually observed using video cameras or other like devices. However, typically such visual inspection is accomplished via video cameras during routine surveys, or, in a few instances, via permanently deployed subsea camera systems. In both approaches, the detection of breakage or movement of subsea components, such as pipes, relies on the observational skills of the camera operator. This makes leak detection using systems that employ only such camera based observation highly dependent on the skill, subjective judgment and diligence of the operators of such systems, and generally makes them less desirable for long-term, continuous monitoring of subsea facilities to detect leaks.
The present invention is directed to various devices and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.